Processes for treating cellulosic textiles with acid colloids of methylolmelamine



United States Patent 3,119,715 Patented Jan. 28, 1984 Office PROCESSES FOR TREATING CELLULOSIC TEX- TILES WITH ACID COLLOIDE? F METHYLQL- MELAMINE Wilson A. Reeves, Metairie, La., and Wilfred N. Berard, Ashland, Mass, assiguors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Apr. 6, 1962, Ser. No. 185,731

11 Claims. (Cl. 117-4385) (Granted under Title 35, U.S. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the World for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the use of acid colloids of aminoplast resin formers for treating cellulosic textiles. More particularly, the invention provides improved processes for treating cellulosic textiles with acid colloids of methylolmelamine to produce cellulosic textile fibers containing polymerized methylolmelamine. The cellulosic textiles produced by the improved processes of the invention have outstanding resistance to microorganisms, out door weathering, wrinkling, and mussing. The term acid colloid as used herein refers to methylolmelamine molecules which are associated and stabilized in water solution by polar acid groups, and which possess light-scattering properties.

A number of investigators have shown that cellulosic textiles can be made resistant to microorganisms, soil contact, outdoor weather, wrinkling, and mussing by ap plication of methylolmelamines. In those investigations, the methylolmelamine and other aminoplast resins were applied by the conventional process. By conventional process we mean the application of an aqueous system of a resin former and a latent acid catalyst to a textile followed by a dry and a cure at elevated temperatures as presently practiced by the textile industry. As used in the conventional process, these aqueous systems of N- methylol compounds, such as methylolurea and methylolmelamine, are slightly alkaline (pH of about 8).

Another method of using aminoplasts for protection of cellulosic fibrous material from attack by microorganisms has been reported in US. Patent No. 2,763,574. The main dilierence in the method of treatment provided by the aforementioned patent and the conventional method of application is that in the former case the monomer is cured in the presence of water at a temperature not to exceed about 80 C. This is usually accomplished by the use of steam. The time required for curing by this process is generally more than one hour, which is rather inconvenient for many textile finishing plants.

Acid colloids of aminoplast resin formers have been used in the prior art, but not to impart resistance to rot, weather, wrinkle or muss. The colloids used in the prior art are significantly different from the acid colloids we have found useful, even though the starting materials are the same. In the earlier processes the colloids were permitted to age before use, often as much as twenty-four hours, thus allowing rather large polymers or colloidal fibers causing them to stick together, and in this way texparticles to form; these materials coated the cellulosic tiles were stiffened and paper was given great wet strength. Cook [Textile Research J. 24, 197-209 (1954)] observed that a cotton fabric impregnated with an aged acid colloid of methylolmelamine had completely deteriorated when exposed to a 2 Weeks soil burial test. This resistance to rot was much less than when the resin was applied by the conventional method. Nuessle [American Dyestufi Reporter 41, 196-212 (1952)] has shown that aged acid colloids of methylolmelamine do not improve wrinkle resistance of cotton fabrics.

We have found that unexpected and valuable properties can be imparted to a cellulosic textile by impregnating it with an unaged acid colloid of methylolmelamine, then insolubilizing the methylolmelamine by heating to cause polymerization within the fiber. When we say unaged, we mean an acid colloid up to about 4 hours old. The acid colloid is prepared by dissolving the methylolmelamine and an appropriate acid in water to give a solution having a pH between about 2 and about 5. The colloid is water-clear and disperses light. To be effective in imparting the unexpected properties to the textiles, the colloid must be used within about 4 hours after preparation.

The primary object of this invention is to provide processes for modifying cellulosic textiles to produce fabrics with substantially improved physical properties, especially the resistance to mildew and rot caused by microorganisms, resistance to degradation caused by solar radiation encountered in outdoor exposure, and resistance to creasing and mussing. The last two properties are especially desirable properties for textiles intended for use in household and wearing apparel; the other properties are especially desirable for goods that are to be used outdoors such as tents, paulins, awnings, irrigation pipe, and sand bags.

In general, in accordance with this invention, cellulosic textiles that are resistant to microorganisms, solar radiation, crease, and muss are produced by wetting the textile in a freshly prepared aqueous acid colloid solution of methylolmelamine, mechanically removing excess solution from the fabric, drying the fabric and then heating the dry fabric to further polymerize the methylolmelamine. We have found that when cellulosic textiles are treated according to the improved processes of this invention, the insoluble polymeric methylolmelamine occurs in the outer portion of the cell wall of the fibers. This is made possible by use of the acid colloids of methylolmelamine within about 4 hours after the solutions are prepared. The position of the resin in the fibers is in contrast to what is found when the same starting materials are applied by prior art techniques. For example, when using the processes of the present invention the resin occurs mainly in the outer portion of the cell Wall of the treated fibers, whereas the resin merely coats the fibers if the acid colloid is allowed to age for about 24 hours. Methylolmelamines applied to cellulosic fabrics by the conventional process as presently practiced in the textile industry generaily penetrate the entire cell wall of the fiber.

The methylolmelamines suitable for use in this invention are those monomers with the following structure:

X X X N B ax X N X wherein B is a methylol group (CH OH), X is a member of the group consisting of H and CH OH. These materials are made by reacting formaldehyde with melamine. Details for the preparation of the methylolmelamines are published and lgnown to those skilled in the art. For use in this invention, the melamine nucleus may contain as few as one N-mcthylol group and as many as six N-methylol groups, or a mixture of N-methylolmelamines. Substantial amounts of polymeric methylolmelamines mixed with the monomers are undesirable, but small amounts (up to about of water-soluble polymeric methylolmelamines do not greatly reduce the utility of the monomers. Methylated methylolmelamines are not suitable for use in this invention.

The technique of application of the acid colloids of the methylolmelamines to textiles consists of wetting the textile with the acid colloid, mechanically removing excess liquid, drying and curing the goods. All of these steps can be conveniently carried out with conventional textile finishing equipment. In order to insure uniform wetting, wetting agents like the cationic, anionic and nonionic types can be added to the acid colloid solution. The wet pickup of the colloid solution is not critical; it may be as low as about 60% or as high as about 110%. The drying time and temperature are not critical, but it is preferable to dry the wet, treated textile at a temperature from about 60 C. to 100 C. just long enough to decrease the moisture content to less than about The drying and curing can be carried out in a single operation. In this case the curing begins as soon as sufficient Water is driven out of the textile. Curing temperatures between about 120 and 170 C. can be employed. The preferred curing temperature is about 140 C. for about 4 minutes for textiles that Weigh about 4 oz. per square yard. Somewhat longer times or higher temperatures are employed for heavier fabrics. Curing can be carried out at 170 C., but at this high temperature the tensile strength of the fabric is reduced.

Following the curing operation, it is desirable to waterwash the fabric to remove any unreacted chemicals. The Washing operation can be conveniently carried out using the procedures and equipment conventionally employed for the water-washing of textiles.

The amount of methylolmelamine that is polymerized inside the fibers can be controlled by the operator, depending upon the specific properties desired in the treated cellulosic fabric. For example, with cotton fabric, excellent wrinkle and muss resistance is obtained with as little as 4% weight increase (resin add-on) but not more than about 12% add-on, whereas for good rot resistance (resistance to microorganisms), at least eight percent resin must be added onto the fabric. The preferred add-on for obtaining crease and muss resistance is from 4% to about 10%. For rot and weather-resistance, the preferred add-on is from 8% to about 14%.

Acids suitable for adding to solutions of the methylolmelamines for the formation of acid colloids used in this invention include the following: formic acid; mixtures of formic acid and an acid salt; mixtures of glycolic acid and an acid salt; mixtures of acetic acid and an acid salt; and the like. The preferred pH range for the acid colloid solutions is from about 2 to about 5. Salts of strong mineral acids, either singly or in combination, are generally suitable acid salts to use in the present invention. Small amounts of the acid salts (from about 1% to about 5%, based on the weight of methylolmelamine) must be used in conjunction with the organic acids when only small amounts of the acids (that is, concentrations up to about 4% by weight of the acids in the acid colloid treating system) are employed. However, when about 5% or more of formic acid is used with the methylolmelamine, the acid salts are not needed in the acid colloid treating system. Acetic and glycolic acids must be used in conjunction with an acid salt, otherwise the resin add-on is rather low. The use of about 20% by weight of formic acid in the acid colloid system is generally preferred, because the colloids made with this high concentration of acid have good stability. Although these treating solutions are stable for very long periods of time, usually at least eight hours, they must be used within about 4 hours after preparation in order to produce fabrics with outstanding resistance to microorganisms, wrinkles, and muss. Fabrics finished With acid colloids prepared using about 2% by weight of the organic acids and about 2% by weight of FeCl: or CrCl are outstanding, in this respect, but in this case the colloids must be used within about 30 minutes after preparation because after about 30 minutes an insoluble precipitate of polymeric methylolmelamine begins to form in the treating solution.

The process of this invention can be used to treat substantially any hydrophilic fibrous cellulosic material such as cotton, rayon such as viscose rayon, ramie, jute, paper, cardboard and the like materials which contain at least two free hydroxyl groups per anhydroglucose unit of the cellulose and which can be impregnated with a liquid, dried, and cured.

The following examples are illustrative of the details of at least one method of practicing the present invention. All parts and percentages are by Weight.

EXAMPLE 1 Seventeen aqueous solutions of methylolmelamine were prepared, each containing 17% mcthylolmelaminc, and then either an acid salt (latent acid catalyst) or a free acid or a combination of both was added to the methylolmelamine solutions. The methylolmelamine contained from one to six methylol groups per molecule, with an average of three methylol groups per molecule. The composition of the various solutions are given in Table I. For example, solution No. 1 contained methylolmelamine and a commercial alkanolamine hydrochloride (specifically, 2 amino 2 methyl-l-propanol hydrochloride), whereas solution No. 2 contained 2.3% acetic acid in addition to these two components. Thus, some of the solutions contained only a latent acid catalyst and others contained a latent acid catalyst plus a free acid in addition to the methylolmelamine. The solutions containing free acid were acid colloids and possessed the property of dispersing a beam of light. Where the latent acid catalyst was used, 1.75% based upon the weight of methylolmelamine was used.

Within thirty minutes after preparation, the solutions were used to treat cotton print cloth. To do this, the fabric was padded in the solution then hung in a forced draft oven to dry at about C. The dry fabric, which contained about 15% or less moisture, was cured by heating for 4 minutes at C. and then washed in hot water and dried. All the finished fabrics, except the one treated with solution No. 15 of Table I, contained about 12% resin add-on.

It is readily apparent from the data in Table I that those fabric samples which had been treated with the solutions containing acetic acid were much more rcsistant to the microorganisms found in the soil bed. (Soil burial tests were carried out according to American Standards for Testing Materials.) In general, the fabric samples finished with methylolmelamine solutions containing both a latent acid catalyst and acetic acid retained as much strength after 15 weeks in the soil bed as the samples finished with methylolmelamine solutions containing only the latent acid catalyst after 4 weeks in the same soil bed.

Methylolmelamine solution used to finish the fabric Strength retained (percent) after soil burial Solution Latent acid catalyst added Free acid added 2 wks. 4 wks. 6 wks. 12 wks. 15 wks.

No. (percent) 2-arnino-2-methyl-1-propanol None 91 33 19 hydrochloride. Acetic (2.3%) 100 100 95 65 24 None 52 13 3 100 100 100 59 30 None 95 49 24 Acetic (2.3%) 100 100 100 47 26 None 50 12 10 Acetic (23%)-..- 100 100 96 60 29 None 71 30 11 Acetic (2.3%) 100 100 100 66 38 94 23 100 100 100 83 47 100 27 16 100 100 100 59 35 None 100 100 56 20 9 wks. 18 wks. CrOh" do 100 100 100 100 94 9 wks 18 wks. FeCl; do 100 100 100 90 1 The fabric treated with this solution contained only 9% resin add-on after finishing.

The seventeen samples of resin-treated fabric prepared as described above were examined for resistance to outdoor weathering. A sample of untreated cotton print.

cloth was also tested for comparative purposes. The weather exposure tests were conducted in an unshaded location, and the samples were exposed on open-backed wooden racks facing south at an angle of 45 from the vertical and at a minimum distance of inches above the ground. The fabrics were sampled at two-month intervals and the breaking strength of the samples was determined. Table II gives the results of the tests in terms of percent strength retained after the various periods of outdoor exposure. The fabric sample numbers of Table II correspond to the solution numbers of Table I. For example, fabric sample No. 1 was produced using solution No. 1. It is apparent from the data of Table II that all of the resin-treated samples except the one (No. 17) containing FeCl were considerably more resistant to outdoor weathering than was untreated cotton.

Table II.--Weather Resistance of Print Cloth Treated With Methylolmelamine Solutions Described in Table l An acid colloid solution, having the property of dispersing a beam of light, was made by dissolving 17 parts of methylolmelamine and 20 parts of formic acid in 63 parts of water. A portion of the solution was used within about 10 minutes after preparation to finish 80 x 80 cot-ton print cloth. Other portions were used at 2, 4, 5, 6, and 7 hours after the colloid solution was prepared.

The fabrics were wet by use of a textile padder and then dried and cured. The drying was done at about 80 C. until the moisture content of the fabric was below 15%, and the curing was done at about 145 C. for four minutes. After washing the samples in hot water for 30 minutesand drying, they were tested in the soil bed as described in Example 1. Each of the samples of fabric contained about 12% resin add-on. The results of the soil bed tests are shown in Table III. The importance of using the colloids shortly after preparation is readily apparent.

Table III.R0t Resistance of Print Cloth Finished With 40 Formic Acid Colloids of T rimethylolmelamine (12% Resin Add-On) Breaking strength retained (percent after Soil Burial Age of Colloid Used 2 4 6 12 18 21 wks wks. wks. wks. wks. wks.

Freshly prepared 100 100 100 100 100 100 iter 2 hours 100 100 100 100 92 78 After 4 hours. 100 100 100 63 21 After 5 hours 100 100 75 as 24 After 6 hours 100 100 76 21 7 After 7 hours 97 87 62 15 EXAMPLE 3 same as that described in Example 2. For the 12% resin.

add-on, the fabric was treated with a solution containing 17% methylolmelamine and 20% formic acid. To get the lower resin add-on more dilute solutions of methylolmelarnine were used, but the concentration of formic acid was held at about 20%. For example, 3% resin add-on was obtained by using a solution containing 3.4% me-thylolmelamine and 20% formic acid. Table IV gives the percent strength retained by samples treated with the various resin add-ons after the indicated periods of soil burial conducted as described in Example 1. The table shows that excellent wot resistance is obtained with 10% or more resin. 8% of the resin applied by use of the acid colloid (Table IV) was equivalent to 12% resin applied by the conventional technique as shown by sample 1 in Table I, Example 1.

Table IV.-Influence of Add-n of Formic Acid Colloid Upon Degree of Rot Resistance Five samples of a lightweight cotton cloth were treated with formic acid colloids of methylolmelamine as in Example 3. The finished fabrics contained 2, 4, 7, 9, and 12% resin add-on. Another piece of the same cotton cloth was finished with the same methylolmelamine using the conventional techniquein this case the methylolmelamine Was dissolved in water, then a latent acid catalyst (2-amino-2-methyl-l-propanol hydrochloride) was added and the fabric was padded in the slightly alkaline (pH of about 8) solution and then dried, cured and washed in exactly the same manner as used for the acid colloid, giving treated fabric with 10% resin add-on. Both the acid colloid finished samples and the conventional finished sample had a good hand. Table V shows that the acid colloid finished fabric with 4% resin add-on had a crease recovery (A.S.T.M. Test D1295-53T) of 276 (W+F) degrees which is better than was obtained with 10% resin when applied by the conventional technique. With 7% and more of the resin applied by the acid colloid technique, the wrinkle resistance (crease recovery) was outstanding. The samples with 4% or more of the acid colloid finish remained essentially wrinkle-free (muss resistant) after they were washed in a home-type washing machine and then dried in an electrically heated tumble clothes dryer.

T able V.-S0me Physical Properties of Acid Colloid Finished Cotton Clot/z Two acid colloid solutions (A and B) of methylolmelamine were made as follows: Solution A was made by dissolving 8.2 parts of methylolmelamine and 20 parts of formic acid in 72 parts of water. Solution B was made by dissolving parts of methylolmclamine and parts of formic acid in 65 parts of water. These solutions were used within one hour after preparation to finish cotton broadcloth. The cloths were padded, dried and cured as described in Example 2. The fabric finished with solution A was designated fabric A; the fabric treated in solution B was designated fabric B. Fabric A contained 6% weight add-on and fabric B had 10% weight add-on. Both fabrics were rot resistant, fabric B having outstanding rot resistance. The wet crease recovery angle (W+F) for A was 265, whereas B had a wet crease recovery angle of 280 (W+F). These fabrics were washed in a conventional home type washing machine then tumble dried in a home type automatic clothes dryer. Both fabrics were wrinkle free after the drying operation.

This application is a continuation-impart of applica- 8 tion bearing Serial No. 799,389, filed March 13, 1959, now abandoned.

We claim:

1. A process comprising wetting a hydrophilic fibrous cellulosic material containing at least two free hydroxyl groups per anhydroglucose unit of the cellulose molecules with an aqueous acid colloid solution of a monomeric methylolmelamine having the general formula wherein B is a methylol group (-CH OH), and X is a member of the group consisting of H and CH OH, removing excess liquid from the thus-wetted cellulosic material, drying and curing the resulting cellulosic material to polymerize the methylolmelamine in the outer portion of the cell walls of the fibers of the cellulosic material, and thereafter removing unreacted chemicals from the thus dried-and-cured cellulosic material to obtain a modified cellulosic material which possesses resistance to mildew and rot caused by microorganisms, resistance to degradation caused by solar radiation encountered in outdoor exposure, and resistance to creasing and mussing.

2. A process comprising wetting a hydrophilic fibrous cellulosic material containing at least two free hydroxyl groups per anhydroglucose unit of the cellulose molecule with an aqueous acid colloid solution of a monomeric methylolmelamine having the general formula wherein B is a methylol group (-CH OH), and X is a member of the group consisting of -H and --CH OH, said aqueous acid colloid solution having a pH between about 2 and 5 and containing from zero to not more than about 10% of water-soluble polymeric methylolmelamines, removing excess liquid from the thus-wetted cellulosic material, drying the resulting cellulosic material at a temperature of about from 60 to C. until the moisture content thereof is reduced to below about 15%, said drying simultaneously initiating polymerization of the methylolmelamine monomer, curing the thus-dried cellulosic material at a temperature of about from to C. to complete the polymerization of the methylolmelamine in the outer portion of the cell walls of the fibers of the cellulosic material, and thereafter removing unreacted chemicals from the thus-cured cellulosic material to obtain a modified cellulosic material which possesses resistance to mildew and not caused by microorganisms, resistance to degradation caused by solar radiation encountered in outdoor exposure, and resistance to creasing and mussing.

3. The process of claim 2 wherein the aqueous acid colloid solution of the monomeric methylolmelamine contains formic acid in a concentration of at least about 5% to yield a modified cellulosic material having a methylolmelamine polymer add-on of about from 4% to 12% and possessing crease and muss resistance.

4. The process of claim 2 wherein the aqueous acid colloid solution of the monomeric methylolmelarninc contains formic acid in a concentration of at least about 5% to yield a modified cellulosic material having a methylolmelamine polymer add-on of about from 8% to 14% and possessing resistance to mildew and rot caused by microorganisms and resistance to degradation caused by solar radiation encountered in outdoor exposure.

5. The process of claim 2 wherein the aqueous acid colloid solution of the monomeric methylolmelamine contains an organic acid selected from the group consisting of formic acid and acetic acid in a concentration ranging up to about 4% by weight of the acid in the acid colloid solution, and a latent acid catalyst comprising a salt of a strong mineral acid in a concentration of about from 1% to based on the weight of the methylolmelamine in the solution.

6. The process of claim 5 wherein the cellulosic material is a textile fabric, the organic acid is used in a concentration of about 2% by weight, of the acid colloid, and the latent acid catalyst is FeCl which is employed in a concentration of about 2% by weight, based on the weight of the monomeric methylolmelamine.

7. The process of claim 5 wherein the cellulosic material is a textile fabric, the organic acid is used in a conentration of about 2% by weight of the acid colloid, and the latent acid catalyst is CrCl which is employed in a concentration of about 2% by weight, based on the weight of the monomeric methylolmelamine.

8. A modified fibrous cellulosic material containing polymerized methylolmelamine in the outer portion of the cell walls of the fibers of the material in an amount ranging from about 4% to 14%, by weight, of the original unmodified fibrous cellulosic material, said modified fibrous cellulosic material possessing resistance to mildew and rot caused by microorganisms, resistance to degradation caused by solar radiation encountered in outdoor exposure, and resistance to creasing and mussing.

9. A modified fibrous cellulosic material containing polymerized methylolmelamine in the outer portion of the cell walls of the fibers of the material in an amount ranging from about 4% to 12%, by weight, of the original unmodified fibrous cellulosic material, said modified fibrous cellulosic material possessing resistance to creasing and mussing.

10. A modified fibrous cellulosic material containing polymerized methylolmelamine in the outer portion of the cell walls of the fibers of the material in an amount ranging from about 8% to 14%, by weight, of the original unmodified fibrous cellulosic material, said modified fibrous cellulosic material possessing resistance to mildew and rot caused by microorganisms and resistance to degradation caused by solar radiation encountered in outdoor exposure.

11. A process comprising Wetting a hydrophilic fibrous cellulosic material containing at least two free hydroxyl groups per anhydroglucose unit of the cellulose molecule with an aqueous acid colloid solution of a monomeric methylolmelamine having the general formula wherein B is a methylol group (CH OH), and X is a member of the group consisting of -H and -CH OH, said aqueous acid colloid solution having a pH between about 2 and 5, containing from zero to not more than about 10% of water-soluble polymeric methylolmelamines, and being used to wet said cellulosic material within about 30 minutes to 2 hours after its preparation, removing excess liquid from the thus-wetted cellulosic material, drying the resulting cellulosic material at a temperature of about from to C. until the moisture content thereof is reduced to below about 15%, said methylolmelamine monomer, curing the thus-dried cellulosic material at a temperature of about from to drying simultaneously initiating polymerization of the C. to complete the polymerization of the methylolmelamine in the outer portion of the cell walls of the fibers of the cellulosic material, and thereafter removing unreacted chemicals from the thus-cured cellulosic material to obtain a modified cellulosic material which possesses resistance to mildew and rot caused by microorganisms, resistance to degradation caused by microorganisms, resistance to degradation caused by solar radiation encountered in outdoor exposure, and resistance to creasing and mussing.

References Cited in the file of this patent UNITED STATES PATENTS 2,423,428 Pollard July 1, 1947 2,485,080 Wohnsiedler et al Oct. 18, 1949 2,661,262 Folkers Dec. 12, 1953 2,763,574 Ruperti Sept. 18, 1956 2,901,463 Hurwitz Aug. 25, 1959 

1. A PROCESS COMPRISING WETTING A HYDROPHILIC FIBROUS CELLULOSIC MATERIAL CONTAINING AT LEAST TWO FREE HYDROXYL GROUPS PER ANHYDROGLUCOSE UNIT OF THE CELLULOSE MOLECULES WITH AQUEOUS ACID COLLOID SOLUTION OF A MONOMERIC METHYLOLMELAMINE HAVING THE GENERAL FORMULA 